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Despite recent advancements in the physics and chemistry of high temperature air flows, large uncertainties remain to be reduced. Numerical procedures are necessary for advancement of understanding and modeling of their effects. Unfortunately, they have complex effects on the complex shapes of orbiter like U.S. Shuttle Orbiter and Hermes, and on the flight-test results, where they are mixed together with other complex phenomena, related to viscous flows.

For clarification of the engineering implication of modeling uncertainties, some results of comparisons are given for different physical and chemical modeling on the simple shape of an AOTV. They emphasize the effect on the pitching moment and on the heat transfer, and give correlated variations in the bow shock wave, conclusions are given on the research to be pushed, and its inclusion in the Hermes aerothermal research program, presently in progress amongst the European scientific community. Such a research is therefore a part of the necessary aerothermal technology for future reentry vehicles.